This invention relates to improved gas-liquid contact apparatus in which a fractionation tower or other vessel is provided with a packing formed of a vertical stack of grids.
Packing materials are used in chemical processing apparatus to provide (a) a supporting surface for the downward flow of liquid and (b) openings for the upward flow of gases. Liquid which is introduced to the upper end of the packing flows downwardly as a thin film on the surfaces of the packing material. Gaseous vapors are injected into the lower end of the vessel and ascend through the openings in the packing material, moving through the vessel in intimate contact with the liquid film on the surface of the packing. Such contact between the liquid and gas can produce mass transfer, a chemical reaction, heat exchange and/or scrubbing of the gaseous stream.
The invention described in this specification is primarily envisioned for use in heat exchange sections of fractionation towers, such sections usually being located where there is a liquid flow rate in relation to the gas flow rate. This occurs in pump-around sections and flash sections of vacuum fractionating towers where direct contact between the vapor and the liquid are used to remove heat from the ascending vapor. Ideally, this can be achieved with a minimal amount of entrainment of liquid droplets into the gaseous stream, a minimal pressure differential between the incoming gases and the outgoing gases, and a continuous downward flow of liquid which assures that effective heat exchange will continue throughout a wide range of gas flow rates.
A variety of packings are available for the heat exchange sections of fractionation towers but, to the inventor's knowledge, all fall short of meeting the ideal characteristics listed above. Such packings may provide downwardly-facing surfaces which are shaped or dimensioned so as to provide an undue pressure drop in the gaseous stream, they may inherently release liquid droplets which cause splashing and promote entrainment of liquid in the gaseous stream, or they may have other shortcomings. The objectives of the present invention are to provide a superior packing material which deters entrainment, minimizes pressure drop and provides an effective contacting relationship between the gas and liquid.
A single-layer liquid distributor for use with random packings is disclosed by the Moore et al U.S. Pat. No. 4,171,333. Some earlier packing materials are disclosed in the following U.S. Patents:
U.S. Pat. No. 100,766, Huntington PA1 U.S. Pat. No. 556,811, Dold PA1 U.S. Pat. No. 1,118,267, Burhorn PA1 U.S. Pat. No. 2,591,343, Eld PA1 U.S. Pat. No. 2,885,195, Haselden PA1 U.S. Pat. No. 2,998,234, Haselden PA1 U.S. Pat. No. 3,533,609, Brandt et al. PA1 U.S. Pat. No. 3,079,134, Winn PA1 U.S. Pat. No. 3,343,821, Winn et al.
A primary objective of the present invention is to provide a packing which is effective and results in minimal gaseous pressure drop and a minimal entrainment. Additionally, it is an objective to provide a packing which is relatively uncomplicated, easily manufactured and structurally sound.
The invention claimed in this application is an improvement to the packing disclosed in U.S. patent application Ser. No. 267,494 filed May 27, 1981. However, in addition to the attributes of the previously disclosed packing, the present invention provides a packing which requires less material for manufacture.